Numerous past studies have considered the problem of determining the existence of laryngeal pathology using acoustic measures such as average pitch period or amplitude perturbation of sustained vowels. Voiced speech is acoustically modeled by the linear filtering action of the vocal tract on the driving function, and laryngeal pathology may acoustically affect the driving function, but not the vocal tract. A laryngeal pathology that causes a voice change might be detected at an early stage of pathological involvement if the resultant speech is analyzed by removing or "inverse filtering" the vocal tract's effects to obtain the driving function. Acoustic measures based on the driving function appear to contain more information related to the pathology than acoustic measures based on the speech waveform. The goal of this research program is to study the properties of certain features measured from inverse filtered sustained vowels, with particular interest toward formulating and evaluating clinical procedures, primarily for early acoustic detection of laryngeal pathology, but also for acoustic assessment of voice therapy. These features will be compared with analogous features measured directly from the speech waveform to determine the benefits of removing the acoustic contributions of the vocal tract from the speech waveform. Through collaboration with nearby medical centers, vowel samples categorized by age and sex, and type and degree of laryngeal pathology, will be obtained.